Indeno-fused naphthol materials, including ethers and esters of indeno-fused naphthols, have many uses, such as intermediates in the synthesis of photochromic compounds and materials, such as indeno-fused naphthopyrans. Photochromic materials, such as indeno-fused naphthopyrans, in response to certain wavelengths of electromagnetic radiation (or “actinic radiation”), typically undergo a transformation from one form or state to another form, with each form having a characteristic or distinguishable absorption spectrum associated therewith. Typically, upon exposure to actinic radiation, many photochromic materials are transformed from a closed-form, which corresponds to an unactivated (or bleached, e.g., substantially colorless) state of the photochromic material, to an open-form, which corresponds to an activated (or colored) state of the photochromic material. In the absence of exposure to actinic radiation, such photochromic materials are reversibly transformed from the activated (or colored) state, back to the unactivated (or bleached) state. Compositions and articles, such as eyewear lenses, that contain photochromic materials or have photochromic materials applied thereto (e.g., in form of a photochromic coating composition) typically display colorless (e.g., clear) and colored states that correspond to the colorless and colored states of the photochromic materials contained therein or applied thereto.
Indeno-fused naphthol materials are typically prepared by a synthetic scheme involving the reaction of a benzophenone with a dialkyl succinate, which is typically referred to as a Stobbe reaction route. When unsymmetrical benzophenones are used, a mixture of indeno-fused naphthol materials typically results from the Stobbe reaction route. The mixture of indeno-fused naphthols typically must be separated so as to isolate the desired indeno-fused naphthol. The isolated indeno-fused naphthol can then be used in subsequent reactions (e.g., in the synthesis of photochromic indeno-fused naphthopyrans). The separation and isolation steps generally result in significantly reduced yields relative to the desired indeno-fused naphthol materials.
Some photochromic materials, such as photochromic indeno-fused naphthopyrans can be expensive, and in light of economic considerations, reducing the costs associated with synthesizing such materials is typically desirable.
It would be desirable to develop new methods of making indeno-fused naphthol materials. In addition, it would be desirable that such newly developed methods provide improved yields, and economic benefits relative to previous synthetic methods.